The present invention relates to chemical mechanical planarization (“CMP”) polishing compositions (CMP slurries, CMP composition or CMP formulations are used interchangeably) used in the production of a semiconductor device, and polishing methods for carrying out chemical mechanical planarization. In particular, it relates to polishing compositions comprising composite abrasive particles that are suitably used for polishing patterned semiconductor wafers that composed of oxide materials.
Silicon oxide is widely used as dielectric materials in semiconductor industry. There are several CMP steps in integrated circuit (IC) manufacturing process, such as shallow trench isolation (STI), inter-layer dielectric (ILD) CMP and gate poly CMP etc. Typical oxide CMP slurry involves: abrasive, with or without other chemicals. Other chemicals could be dispersants to improve slurry stability, booster to increase removal rate, or inhibitors to decrease removal rate and to stop on the other film, for example, SiN for STI application.
Among common abrasives used in CMP slurries, such as silica, alumina, zirconia, titania and so on, ceria is well-known for its high reactivity toward silica oxide and is widely used in STI CMP slurry for the highest oxide removal rate (RR) due to the high reactivity of ceria to silica.
Cook et al. (Lee M. Cook, Journal of Non-Crystalline Solids 120 (1990) 152-171) proposed a ‘chemical tooth’ mechanism to explain this extraordinary property of ceria. According to this mechanism, when ceria particles are pressed onto silicon oxide film, ceria breaks down silica bonds, forms a Ce—O—Si structure and thus cleavage silica from the surface.
Most of the ceria used in CMP industry are manufactured from calcinations-wet milling process. The resulted ceria has sharp edges and very wide size distribution. It also has very large “large particle count” (LPC). All of these are believed to be responsible for defects and low yields, especially scratch after the wafer is polished. This is confirmed from IC fabs that are suffering from defects with ceria based slurries.
Besides calcined ceria, some particle companies have commercial products with colloidal ceria. Colloidal ceria is made from ceria precursor in aqueous system. Compared to calcined ceria (top-down process), colloidal ceria is bottom up process. Colloidal ceria has a much narrower size distribution and better controlled shapes. However, due to the crystal growth habit in aqueous system, colloidal ceria still has sharp edges. LPC of colloidal ceria is comparable to that of calcined ceria.
As the semiconductor technology advances to smaller feature sizes, the specifications on allowable size and number of defects on post-polish also become more challenging. Defects typically comprise scratches, slurry residues and residual film residues. The properties of polishing pads critically affect polishing results during chemical mechanical polishing (CMP) of integrated circuit substrates. One of the critical parameters of the CMP pads that defines the performance is pad hardness or elasticity. It is known that softer pads cause reduced scratches on surface (e.g. Hsein et al. Microelectronic Engineering, vol 92, 2012, pp 19-23). It will therefore be highly beneficial to use softer pads to reduce scratch defects in critical CMP processes such as shallow trench isolation. However, it is known that softer pads result in lower removal rates (e.g. Castillo-Mejia et al., Journal of Electrochemical Society, Vol. 150 (2), 2003, pp G76-G82). Also it is known that softer pads have an undesirable impact on post-polish topography of patterned wafers (e.g. L. Wu, Journal of Electrochemical Society, Vol. 153 (7), 2006, pp. G669-G676). Because of these limitations of soft pads, STI CMP process is carried out on harder CMP pads such as IC1000 or IC1010. Compensating for lower removal rates on soft pads by increasing abrasive particle loading would lead high defectivity. As a result, for critical applications such as STI, it is very challenging to achieve a combination of high removal rates, low defectivity and low topography on soft pad.
Therefore, there are significant needs for CMP compositions, methods, and systems that can offer higher removal rate (especially on soft polishing pad); low dishing and low defects.